2023 Fiscal Year Annual Research Report
| Project/Area Number |
23H01359
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| Allocation Type | Single-year Grants |
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| Research Institution | National Institute for Materials Science |
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Principal Investigator |
SANG Liwen 国立研究開発法人物質・材料研究機構, ナノアーキテクトニクス材料研究センター, 主幹研究員 (90598038)
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| Project Period (FY) |
2023-04-01 – 2027-03-31
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| Keywords | GaN / superlattices / thermal dissipation |
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| Outline of Annual Research Achievements |
The thermal phonon transportation in superlattices has been investigated. Using metal organic chemical vapor deposition, high-quality InGaN/GaN superlattices, AlGaN/GaN superlattices are prepared. The interface is very sharp into nanometer level by transmission electron microscopy. By changing period thickness in superlattics, the crossover from incoherent to coherent phonon transport were determined. It is found that, when the period thickness is lower than phonon mean free path, coherent phonon transport was achieved. The thickness is also influenced by the quality, such as dislocations in superlattices. At the high-density interface, the coherence starts to be disturbed due to larger strain and degraded interface morphology. Moreover, highly orientated polycrystalline diamond film was deposited on GaN template by micro-plasma chemical vapor deposition.The diamond film has a thermal conductivity approaching 250W/mK when the thickness is ~1 um, belonging to the high level for polycrystalline diamond film. The optimized superlattices were introduced as interlayer between GaN and diamond as the thermal dissipation solution. The thermal boundary resistance was achieved as low as 4m2K/GW, which is much lower than those with SiNx of AlN interlayers.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The crossover from incoherent to coherent transport in GaN-based superlattices was determined. This will be helpful for the future device design.
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| Strategy for Future Research Activity |
We will further optimize the interface of superlattices by MOCVD, to reduce the interface defects in InAlN/GaN and AlGaN/AlN superlattices. The measurement and analysis of the thermal property across interface will be necessary. Furthermore, theoretical calculation on phonon transport is also important
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